From nobody Tue Sep 9 17:32:20 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6794EC636D6 for ; Wed, 22 Feb 2023 03:17:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231176AbjBVDRH (ORCPT ); Tue, 21 Feb 2023 22:17:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230109AbjBVDQx (ORCPT ); Tue, 21 Feb 2023 22:16:53 -0500 Received: from loongson.cn (mail.loongson.cn [114.242.206.163]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 61F976EAC for ; Tue, 21 Feb 2023 19:16:51 -0800 (PST) Received: from loongson.cn (unknown [113.200.148.30]) by gateway (Coremail) with SMTP id _____8AxII8gifVjWm8DAA--.1484S3; Wed, 22 Feb 2023 11:16:48 +0800 (CST) Received: from bogon.localdomain (unknown [113.200.148.30]) by localhost.localdomain (Coremail) with SMTP id AQAAf8DxUuUbifVj9l84AA--.2774S6; Wed, 22 Feb 2023 11:16:48 +0800 (CST) From: Youling Tang To: Huacai Chen , Xi Ruoyao , Jinyang He Cc: Xuerui Wang , loongarch@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v6 4/5] LoongArch: Add support for kernel relocation Date: Wed, 22 Feb 2023 11:16:42 +0800 Message-Id: <1677035803-7932-5-git-send-email-tangyouling@loongson.cn> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1677035803-7932-1-git-send-email-tangyouling@loongson.cn> References: <1677035803-7932-1-git-send-email-tangyouling@loongson.cn> X-CM-TRANSID: AQAAf8DxUuUbifVj9l84AA--.2774S6 X-CM-SenderInfo: 5wdqw5prxox03j6o00pqjv00gofq/ X-Coremail-Antispam: 1Uk129KBjvJXoWxKr4xCrW3ZFWUZr4kZFyUtrb_yoWfGFyxpr Zrur4kJF45GFn3Z34Dt34kuryUJan7Ww12ganxK34rAF12vFyUXrWkZr9rXF1jqw4kXFWF gFyfK342vF4UAaDanT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUj1kv1TuYvTs0mT0YCTnIWj qI5I8CrVACY4xI64kE6c02F40Ex7xfYxn0WfASr-VFAUDa7-sFnT9fnUUIcSsGvfJTRUUU b28YFVCjjxCrM7AC8VAFwI0_Jr0_Gr1l1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s 1l1IIY67AEw4v_Jrv_JF1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xv wVC0I7IYx2IY67AKxVW5JVW7JwA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwA2z4 x0Y4vEx4A2jsIE14v26r4UJVWxJr1l84ACjcxK6I8E87Iv6xkF7I0E14v26r4UJVWxJr1l e2I262IYc4CY6c8Ij28IcVAaY2xG8wAqjxCEc2xF0cIa020Ex4CE44I27wAqx4xG64xvF2 IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jw0_WrylYx0Ex4A2jsIE14v26r4j6F4U McvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwIxGrwCF04k20xvY0x0EwIxGrwCFx2 IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v2 6r106r1rMI8E67AF67kF1VAFwI0_JF0_Jw1lIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67 AKxVW5JVW7JwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IY s7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r4j6F4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr 0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07josjUUUUUU= Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" This config allows to compile kernel as PIE and to relocate it at any virtual address at runtime: this paves the way to KASLR. Runtime relocation is possible since relocation metadata are embedded into the kernel. Signed-off-by: Youling Tang Signed-off-by: Xi Ruoyao # Use arch_initcall Signed-off-by: Jinyang He # Provide la_abs relocati= on draft code --- arch/loongarch/Kconfig | 8 ++ arch/loongarch/Makefile | 5 ++ arch/loongarch/include/asm/asmmacro.h | 13 ++++ arch/loongarch/include/asm/setup.h | 14 ++++ arch/loongarch/kernel/Makefile | 2 + arch/loongarch/kernel/head.S | 5 ++ arch/loongarch/kernel/relocate.c | 108 ++++++++++++++++++++++++++ arch/loongarch/kernel/vmlinux.lds.S | 20 ++++- 8 files changed, 173 insertions(+), 2 deletions(-) create mode 100644 arch/loongarch/kernel/relocate.c diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig index 54bd3dbde1f2..406a28758a52 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -522,6 +522,14 @@ config PHYSICAL_START specified in the "crashkernel=3DYM@XM" command line boot parameter passed to the panic-ed kernel). =20 +config RELOCATABLE + bool "Relocatable kernel" + help + This builds the kernel as a Position Independent Executable (PIE), + which retains all relocation metadata required to relocate the + kernel binary at runtime to a different virtual address than the + address it was linked at. + config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" depends on PROC_FS diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile index ccfb52700237..2aba6ff30436 100644 --- a/arch/loongarch/Makefile +++ b/arch/loongarch/Makefile @@ -71,6 +71,11 @@ KBUILD_AFLAGS_MODULE +=3D -Wa,-mla-global-with-abs KBUILD_CFLAGS_MODULE +=3D -fplt -Wa,-mla-global-with-abs,-mla-local-with-= abs endif =20 +ifeq ($(CONFIG_RELOCATABLE),y) +LDFLAGS_vmlinux +=3D -static -pie --no-dynamic-linker -z notext +KBUILD_CFLAGS_KERNEL +=3D -fPIE +endif + cflags-y +=3D -ffreestanding cflags-y +=3D $(call cc-option, -mno-check-zero-division) =20 diff --git a/arch/loongarch/include/asm/asmmacro.h b/arch/loongarch/include= /asm/asmmacro.h index adc92464afa6..ba99908d7d10 100644 --- a/arch/loongarch/include/asm/asmmacro.h +++ b/arch/loongarch/include/asm/asmmacro.h @@ -668,7 +668,20 @@ .endm =20 .macro la_abs reg, sym +#ifndef CONFIG_RELOCATABLE la.abs \reg, \sym +#else +766: + lu12i.w \reg, 0 + ori \reg, \reg, 0 + lu32i.d \reg, 0 + lu52i.d \reg, \reg, 0 + .pushsection ".la_abs", "aw", %progbits +768: + .dword 768b-766b + .dword \sym + .popsection +#endif .endm =20 #endif /* _ASM_ASMMACRO_H */ diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/as= m/setup.h index 72ead58039f3..68b5b5a1fe8a 100644 --- a/arch/loongarch/include/asm/setup.h +++ b/arch/loongarch/include/asm/setup.h @@ -21,4 +21,18 @@ extern void per_cpu_trap_init(int cpu); extern void set_handler(unsigned long offset, void *addr, unsigned long le= n); extern void set_merr_handler(unsigned long offset, void *addr, unsigned lo= ng len); =20 +#ifdef CONFIG_RELOCATABLE +struct rela_la_abs { + long offset; + long symvalue; +}; + +extern long __rela_dyn_start; +extern long __rela_dyn_end; +extern void *__la_abs_begin; +extern void *__la_abs_end; + +extern void __init relocate_kernel(void); +#endif + #endif /* __SETUP_H */ diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile index 45c78aea63ce..3288854dbe36 100644 --- a/arch/loongarch/kernel/Makefile +++ b/arch/loongarch/kernel/Makefile @@ -31,6 +31,8 @@ endif obj-$(CONFIG_MODULES) +=3D module.o module-sections.o obj-$(CONFIG_STACKTRACE) +=3D stacktrace.o =20 +obj-$(CONFIG_RELOCATABLE) +=3D relocate.o + obj-$(CONFIG_PROC_FS) +=3D proc.o =20 obj-$(CONFIG_SMP) +=3D smp.o diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S index d2ac26b5b22b..499edc80d8ab 100644 --- a/arch/loongarch/kernel/head.S +++ b/arch/loongarch/kernel/head.S @@ -86,6 +86,11 @@ SYM_CODE_START(kernel_entry) # kernel entry point PTR_ADD sp, sp, tp set_saved_sp sp, t0, t1 =20 +#ifdef CONFIG_RELOCATABLE + /* Apply the relocations */ + bl relocate_kernel +#endif + bl start_kernel ASM_BUG() =20 diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/reloc= ate.c new file mode 100644 index 000000000000..feeba0730875 --- /dev/null +++ b/arch/loongarch/kernel/relocate.c @@ -0,0 +1,108 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Support for Kernel relocation at boot time + * + * Copyright (C) 2023 Loongson Technology Corporation Limited + */ + +#include +#include +#include +#include +#include +#include +#include + +#define RELOCATED(x) ((void *)((long)x + reloc_offset)) + +static unsigned long reloc_offset; + +static inline __init void relocate_relative(void) +{ + Elf64_Rela *rela, *rela_end; + rela =3D (Elf64_Rela *)&__rela_dyn_start; + rela_end =3D (Elf64_Rela *)&__rela_dyn_end; + + for ( ; rela < rela_end; rela++) { + Elf64_Addr addr =3D rela->r_offset; + Elf64_Addr relocated_addr =3D rela->r_addend; + + if (rela->r_info !=3D R_LARCH_RELATIVE) + continue; + + if (relocated_addr >=3D VMLINUX_LOAD_ADDRESS) + relocated_addr =3D + (Elf64_Addr)RELOCATED(relocated_addr); + + *(Elf64_Addr *)RELOCATED(addr) =3D relocated_addr; + } +} + +static inline void __init relocate_la_abs(void) +{ + struct rela_la_abs *p; + void *start, *end; + + start =3D &__la_abs_begin; + end =3D &__la_abs_end; + + for (p =3D start; (void *)p < end; p++) { + long v =3D p->symvalue; + union loongarch_instruction *insn =3D (void *)p - p->offset; + u32 lu12iw, ori, lu32id, lu52id; + + lu12iw =3D (v >> 12) & 0xfffff; + ori =3D v & 0xfff; + lu32id =3D (v >> 32) & 0xfffff; + lu52id =3D v >> 52; + + insn[0].reg1i20_format.immediate =3D lu12iw; + insn[1].reg2i12_format.immediate =3D ori; + insn[2].reg1i20_format.immediate =3D lu32id; + insn[3].reg2i12_format.immediate =3D lu52id; + } +} + +void __init relocate_kernel(void) +{ + reloc_offset =3D (unsigned long)_text - VMLINUX_LOAD_ADDRESS; + + if (reloc_offset) + relocate_relative(); + + relocate_la_abs(); +} + +/* + * Show relocation information on panic. + */ +static void show_kernel_relocation(const char *level) +{ + if (reloc_offset > 0) { + printk(level); + pr_cont("Kernel relocated offset @ 0x%lx\n", reloc_offset); + pr_cont(" .text @ 0x%lx\n", (unsigned long)&_text); + pr_cont(" .data @ 0x%lx\n", (unsigned long)&_sdata); + pr_cont(" .bss @ 0x%lx\n", (unsigned long)&__bss_start); + } +} + +static int kernel_location_notifier_fn(struct notifier_block *self, + unsigned long v, void *p) +{ + show_kernel_relocation(KERN_EMERG); + return NOTIFY_DONE; +} + +static struct notifier_block kernel_location_notifier =3D { + .notifier_call =3D kernel_location_notifier_fn +}; + +static int __init register_kernel_offset_dumper(void) +{ + atomic_notifier_chain_register(&panic_notifier_list, + &kernel_location_notifier); + return 0; +} + +arch_initcall(register_kernel_offset_dumper); diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vm= linux.lds.S index 733b16e8d55d..5ec0c008f01d 100644 --- a/arch/loongarch/kernel/vmlinux.lds.S +++ b/arch/loongarch/kernel/vmlinux.lds.S @@ -66,10 +66,21 @@ SECTIONS __alt_instructions_end =3D .; } =20 +#ifdef CONFIG_RELOCATABLE + . =3D ALIGN(8); + .la_abs : AT(ADDR(.la_abs) - LOAD_OFFSET) { + __la_abs_begin =3D .; + *(.la_abs) + __la_abs_end =3D .; + } +#endif + .got : ALIGN(16) { *(.got) } .plt : ALIGN(16) { *(.plt) } .got.plt : ALIGN(16) { *(.got.plt) } =20 + .data.rel : { *(.data.rel*) } + . =3D ALIGN(PECOFF_SEGMENT_ALIGN); __init_begin =3D .; __inittext_begin =3D .; @@ -93,8 +104,6 @@ SECTIONS PERCPU_SECTION(1 << CONFIG_L1_CACHE_SHIFT) #endif =20 - .rela.dyn : ALIGN(8) { *(.rela.dyn) *(.rela*) } - .init.bss : { *(.init.bss) } @@ -107,6 +116,12 @@ SECTIONS RO_DATA(4096) RW_DATA(1 << CONFIG_L1_CACHE_SHIFT, PAGE_SIZE, THREAD_SIZE) =20 + .rela.dyn : ALIGN(8) { + __rela_dyn_start =3D .; + *(.rela.dyn) *(.rela*) + __rela_dyn_end =3D .; + } + .sdata : { *(.sdata) } @@ -133,6 +148,7 @@ SECTIONS =20 DISCARDS /DISCARD/ : { + *(.dynamic .dynsym .dynstr .hash .gnu.hash) *(.gnu.attributes) *(.options) *(.eh_frame) --=20 2.37.3